Analysts have said that "Endgame" could make north of $260 million this weekend in North America, with some who are predicting as much as $300 million. Globally, some analysts say it could make more than $800 million.

Nailing down a precise number has been difficult for industry analysts who are trying to predict this weekend's windfall. Only six films in history have had an opening of $200 million or more in North America and no film has made $300 million in a weekend.

Disney isn't giving an exact number either, but says that it expects "Endgame" to be among the biggest debuts ever. On top of all that, it's opening in a record number of theaters and there are showtimes around the clock in some locations. All of this puts "Endgame" in uncharted territory at the box office and for the analysts trying to gauge the film's performance.

"There's never been anything on this cinematic scale before," Shawn Robbins, chief analyst at Boxoffice.com, told CNN Business. "We're talking about a milestone in pop culture and entertainment that appeals to all demographics on some level. It's an event for nearly everyone."

Film critics, however, are more united. "Endgame" has a 96% Rotten Tomatoes score and the overwhelming buzz is prompting theaters to match the demand: "Endgame" is opening in a record 4,662 theaters in North America on Thursday. It opened in nearly every major international market on Wednesday from France to Iceland to the world's second largest movie market, China, where it made roughly $107.5 million on Wednesday. That's the highest-grossing opening day of all time in China, according to Disney.

It made $169 million overseas on Wednesday.

So why is this film such a big deal?

First of all, it's the final chapter of a story that was ten years in the making. "Iron Man" kicked off the franchise when it debuted on May 2, 2008. Since then, the world has been introduced to Captain America, Thor, Doctor Strange and the Hulk. We also met characters whose own origin stories broke ground and shattered glass ceilings -- not to mention box office records -- with "Black Panther" and "Captain Marvel."

"It's the culmination of a story 21 films in the making," said Jeff Bock, senior analyst at Exhibitor Relations. "And more importantly, 21 critical and box office successes."

"Endgame" will also reveal what happens after the dramatic cliffhanger ending in "Infinity War" where -- without spoiling it for the uninitiated -- a lot of major characters died. Bock thinks this will bring people back for the sequel.

"Thing is, there's going to be so many spoilers going around," he said. "As a fan -- whether casual or ardent -- this is a film that begs to be experienced opening weekend."

That is precisely one of the factors that has made the Marvel Cinematic Universe one of the most successful franchises in movie history. Marvel Studios President Kevin Feige has taken Marvel's library of superheroes and created a web of interconnect characters and plots to keep fans coming back for more. And based on the records that Marvel movies have broken in their debuts, fans are coming in droves on the opening weekend.

Feige's tack has helped Disney and Marvel rake in more than $18.7 billion at the box office.

The projected numbers for "Endgame" are even more impressive considering that it's three hours long -- roughly 30 minutes longer than "Infinity War." Longer films usually means less showtimes and less money for theaters.

But "Endgame" is different, according to Paul Dergarabedian, senior media analyst at Comscore.

"Long movies are traditionally subject to the rules of father time and the limitations in the number of showings per day," he said. "However, that's not the case with 'Endgame,' which has gotten a major assist from theater chains, which are basically showing it 24 hours a day."

AMC Theatres announced on Monday that multiple locationswill stay open all day and nightthis weekend. Seventeen locations willstay open for 72 straight hours from Thursday night through Sunday.

Fandango said Thursday that "Endgame" is the biggest preseller in its history with more than 8,000 showtimes already sold out. AMC also reported that the film set its all-time box office presale record. Online ticket sites crashed and created long online queues to deal with demand when tickets first went on sale earlier this month.

This is good news for the film industry, which could really use some help from superheroes right now.

The domestic box office has been anemic so far this year with ticket sales down about 16% compared to last year.